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g
a
(8) When shale absorbs CO , shale expands and s
2
tends to close the induced cracks. This problem,
which occurs also in coal, is the other problem.
(9) Cost to supply CO and maintain the facilities
2
against corrosion due to carbonic acid. Allam cycle
power
The loop of Allam cycle
and extraction of shale gas
with CO CO2
SC-
2
According to Los Alamos National Laboratory
(Middleton and Carey, 2015), gas recovery from
hydraulic fracturing is relatively poor (20/30%) and
the SC-CO could increase cumulative gas produc-
2
tion by 100% or more compared to water. SC CO2
It means that exhausted shale wells could poten- shale gas gas
tially produce gas just using SC-CO instead of wa- extraction
2
ter (no need to drill because the wells are already CO2 sequestration
existing).
In this moment, with the cost of gas very low, se-
veral shale gas companies are in troubled waters;
using SC-CO in existing exhausted wells to extract Figure 7. Combination of Allam cycle and shale gas ex-
2
shale gas and consequent CO sequestration could traction with SC-CO ; potential power generation from gas
2
2
be the game changer for their business models. without CO emissions.
2
As per Allam cycle, we can consider SC-CO shale
2
gas extraction as a box where the inputs are SC-
CO and suitable proppants and outputs are shale hydraulic fracturing of shale cores using viscous oil, wa-
2
gas and CO sequestration. ter, and liquid carbon dioxide, Rock Mechanics and Rock
2
If we now combine the two boxes (Allam Cycle and Engineering, Vol. 48, No. 4, pp. 1463–1473, doi:10.1007/
SC-CO shale extraction-see Figure 7) we could s00603-015-0774-2 67.
2
have the perfect loop that generates power from Bullis, K. (2013): Fracking with carbon dioxide could help
fossil fuel without CO emissions in the atmosphe- shale gas production in arid areas, http://www.techno-
2
re. logyreview.com/news/512656/skipping-the-water-in-fra-
cking/
Conclusion Bunger, A. P., A. Lakirouhani, and E. Detournay (2010): Mo-
delling the effect of injection system compressibility and vi-
The article has presented a possible synergy scous fluid flow on hydraulic fracture breakdown pressure,
between the Allam cycle (based on supercritical in Proceedings of the 5th International Symposium on In Situ
CO ) and the extraction of shale gas with the same Rock Stress, pp. 59–67.
2
supercritical CO2, output of the Allam cycle. Ishida, T., Aoyagi, K., Niwa, T., Chen, Y., Murata, S., Chen,
The combination of the two technologies could Q. and Nakayama, Y. (2012): Acoustic emission monitoring
lead to power generation from natural gas without of hydraulic fracturing laboratory experiment with supercri-
CO emissions (thanks to the consequent seque- tical and liquid CO , Geophysical Research Letters, Vol. 39,
2
2
stration of CO from the extraction of shale gas with L16309, 2012, doi:10.1029/2012GL052788．
2
supercritical CO ). Ishida, T., Chen, Y., Bennour, Z., Yamashita, H., Inui, S., Na-
2
The article presented some of the current issues gaya, Y., Naoi, M., Chen, Q., Nakayama, Y. and Nagano, Y.
related to extraction with SC-CO , also underlining (2016) : Features of CO fracturing deduced from acoustic
2
2
the advantages of supercritical CO compared to emission and microscopy in laboratory experiments, J. Ge-
2
hydraulic fracturing; particularly, the better recovery ophys. Res. Solid Earth, Vol. 121, No. 11, pp. 8080–8098,
capacity of shale gas extraction and the possibility doi:10.1002/2016JB013365.
of CO sequestration. Ishida, T., Desaki, S., Yamashita, H., Inui, S., Naoi, M., Fujii,
2
H. and Katayama, T. (2017): Injection of supercritical carbon
References dioxide into granitic rock and its acoustic emission monito-
ring, Procedia Engineering, 191, 476-482. (Proc. of Eurock
L. Gandossi, C. Coltri, (2016): “Hydraulic Fracturing and 2017, Paper No. 106, Ostrava, Czech republic, 19–22 June,
other Stimulation Technologies for Shale Gas Exploitation- 2017.) doi:10.1016/j.proeng.2017.05.206
2016- Impiantistica italiana, May-June, p. 21. Ishida, T., Desaki, S., Kishimoto, Y., Naoi, M. and Fujii, H.
E. Giacomazzi, G. Messina (2015): “Exploitation of supercri- (2018): Implosive Acoustic Emissions Induced by Injection
tical CO properties” ENEA. of Supercritical Carbon Dioxide into a Hot Granitic Rock
2
C. Coltri, (2015): “Extracting shale gas with supercritical Mass, Geomechanics and Geodynamics of Rock Masses,
CO ”. La Termotecnica, Sept. 2015, p. 65. 1369–1374, Taylor & Francis Group, London. (Proc. of the
2
Bennour, Z., Ishida, T., Nagaya, Y., Chen, Y., Nara, Y., Chen, International European Rock Mechanics Symposium, EU-
Q., Sekine, K. and Nagano, Y. (2015): Crack extension in ROCK 2018, Saint Petersburg, Russia, 22-26 May 2018),
Impiantistica Italiana - Settembre-Ottobre 2020 57 57